Back to EveryPatent.com
United States Patent |
5,073,597
|
Puydak
,   et al.
|
December 17, 1991
|
Dynamically vulcanized alloys having two copolymers in the crosslinked
phase and a crystalline matrix
Abstract
A dynamically vulcanized alloy composition having improved tensile strength
including a first butyl or halogenated butyl rubber-base elastomer and a
second EPM and/or EPDM elastomer in a matrix of a crystalline polyolefinic
resin, and processes for producing the improved composition.
Inventors:
|
Puydak; Robert C. (Cranbury, NJ);
Hazelton; Donald R. (Chatham, NJ);
Ouhadi; Trazollah (Liege, DE)
|
Assignee:
|
Advanced Elastomer Systems, L. P. (St. Louis, MO)
|
Appl. No.:
|
359060 |
Filed:
|
May 26, 1989 |
Current U.S. Class: |
525/193; 525/194; 525/196; 525/197; 525/198; 525/211; 525/232; 525/237 |
Intern'l Class: |
C08L 015/02; C08L 023/16; C08L 023/26; C08L 009/00; C08J 003/24 |
Field of Search: |
525/193,194,196,237,211,232
|
References Cited
U.S. Patent Documents
4130534 | Dec., 1978 | Coran et al. | 260/33.
|
4130535 | Dec., 1978 | Coran et al. | 525/232.
|
4311628 | Jan., 1982 | Sabet et al. | 525/232.
|
4480074 | Oct., 1984 | Wang | 525/194.
|
4607074 | Aug., 1986 | Hazelton et al. | 525/196.
|
4728692 | Mar., 1988 | Sezaki et al. | 525/74.
|
4801651 | Jan., 1989 | Komatsu et al. | 525/196.
|
4810752 | Mar., 1989 | Bayar | 525/194.
|
4871796 | Oct., 1989 | Komatsu et al. | 525/193.
|
4873288 | Oct., 1989 | Komatsu et al. | 525/193.
|
4912148 | Mar., 1990 | Kim et al. | 525/194.
|
Primary Examiner: Seccuro; Carman J.
Claims
We claim:
1. A dynamically vulcanized thermoplastic composition comprising:
(a) a primary elastomer consisting of bromobutyl rubber;
(b) a secondary elastomer selected from the group consisting of EPM, EPDM
and mixtures thereof; and
(c) a plastic matrix of a crystalline polyolefin comprising polypropylene;
wherein said primary elastomer is substantially fully cured with a peroxide
cure system in combination with a maleimide co-agent; and wherein said
secondary elastomer is substantially fully cured.
2. The composition of claim 1 wherein said crystalline polyolefin is a homo
or copolymer of polypropylene.
3. The composition of claim 2, wherein said secondary elastomer is EPDM.
4. The composition of claim 2, wherein said maleimid co-agent is
m-phenylene bismaleimide.
5. The composition of claim 1, wherein said primary elastomer is from about
10 wt. % to about 90 wt. % based on the weight of the elastomers.
6. The composition of claim 1, wherein said primary elastomer is from about
40 wt. % to about 60 wt. % based on the weight of the elastomers.
7. The composition of claim 1, wherein said secondary elastomer is from
about 10 wt. % to about 90 wt. % based on the weight of the elastomers.
8. The composition of claim 1, wherein said secondary elastomer is from
about 40 wt. % to about 60 wt. % based on the weight of the elastomers.
9. The composition of claim 1, wherein said crystalline polyolefin is from
about 10 wt. % to about 90 wt. % based on the weight of the elastomers and
the crystalline polyolefin.
10. The composition of claim 1, wherein said crystalline polyolefin is from
about 30 wt. % to about 40 wt. % based on the weight of the elastomers and
the crystalline polyolefin.
11. The composition of claim 3, wherein said primary elastomer is from
about 10 wt. % to about 90 wt. % based on the weight of the elastomers.
12. The composition of claim 3, wherein said primary elastomer is from
about 40 wt. % to about 60 wt % based on the weight of the elastomers.
13. The composition of claim 3, wherein said secondary elastomer is from
about 10 wt. % to about 90 wt. % based on the weight of the elastomers.
14. The composition of claim 3, wherein said secondary elastomer is from
about 40 wt. % to about 60 wt. % based on the weight of the elastomers.
15. The composition of claim 3, wherein said crystalline polyolefin is from
about 10 wt. % to about 90 wt. % based on the weight of the elastomers and
the crystalline polyolefin.
16. The composition of claim 3, wherein said crystalline polyolefin is from
about 30 wt. % to about 40 wt. % based on the weight of the elastomers and
the crystalline polyolefin.
17. The composition of claim 1, wherein said primary elastomer and said
secondary elastomer are present in said composition as particles dispersed
in said plastic matrix.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to thermoplastic elastomer blends of polymers that
have been prepared by dynamic vulcanization. The polymer blends comprise a
crystalline polyolefin plastic matrix, such as polypropylene, and two
crosslinked elastomeric polymers wherein one elastomer is butyl or
halobutyl rubber and the other is an ethylene-propylene copolymer-based
rubber.
2. Background
This invention relates to polymer blends which have a combination of both
elastic and thermoplastic properties and which are of significant
commercial interest. Such thermoelastic compositions are generally
obtained by blending an elastomeric composition with a thermoplastic
composition in a way such that the elastomer is intimately and uniformly
dispersed as a discrete phase within a continuous phase of the
thermoplastic composition. These polymer blends have been given the
generic designation of Thermoplastic Olefins ("TPO"). They exhibit some of
the properties of a cured elastomer as well as the reprocessibility of a
thermoplastic resin. The elastomeric characteristics are enhanced if one
component of the blend is a vulcanizable elastomer which is wholly or
partially cross-linked.
The earliest work in the curing of a TPO composition was by Gessler and
Haslett; see U.S. Pat. No. 3,037,954. That patent teaches the concept of
"dynamic curing" wherein a vulcanizable elastomer is dispersed into a
resinous thermoplastic polymer and the elastomer is cured while
continuously mixing and shearing the polymer blend. The resulting blend is
a micro-gel dispersion of cured elastomer in an uncured matrix of resinous
thermoplastic polymer which is known as a dynamically vulcanized alloy
("DVA").
Gessler, '954 discloses compositions comprising polypropylene and a rubber
such as, inter alia, butyl rubber; chlorinated butyl rubber,
polybutadiene, polychloroprene and polyisobutene. Compositions of about 50
to 95 parts polypropylene and about 5 to 50 parts of rubber are disclosed.
The commercially useful DVAs are known to include butyl-based DVA's and
EP/EPDM-based DVAs. The tensile strength of butyl-based DVAs has typically
been lower than that of EP/EPDM-based DVAs when compared at the same Shore
A hardness or polyolefin resin content. Thus, efforts have been directed
towards improving the physical properties of butyl-based DVAs.
U.S. Pat. Nos. 3,758,643 and 3,806,558 disclose TPO type polymer blends
comprising an olefin thermoplastic resin and an olefin copolymer rubber
wherein the rubber is dynamically cured to a partial cure state. The
compositions are reprocessible and result in molded products having good
surface appearance. However, the potential applications of such blends are
limited by their high compression set and/or low softening temperature
resulting from only a partial cure of the rubber. Furthermore, the partial
peroxide cure utilized in such blends is difficult to control from the
standpoint of completeness of reaction, resulting in batch to batch
variations in product properties.
U.S. Pat. No. 4,639,487 to Hazelton, et al. is directed to heat shrinkable
DVAs including an ethylene copolymer resin blended with a butyl or
halogenated butyl rubber. The butyl rubber should be at least partially
dynamically vulcanized to a cured state in the presence of the copolymer.
The invention is restricted in that peroxide cure systems are specifically
excluded. These DVA compositions are said to possess exceptional
resiliency, high coefficient of friction surfaces and low compression set.
U.S. Pat. No. 4,212,787 to Matsuda, et al., however, allows the use of
peroxide cure systems and is directed to the production of partially cured
DVA compositions which include 40-100 wt. % of a peroxide curable
copolymer (such as EPDM); 0-60 wt. % of a peroxide decomposing copolymer
(such as PE and PP); and 5-100 wt. % of a peroxide non-curable rubber,
either polyisobutylene or butyl rubber. One of the objects of the Matsuda
invention is to produce a DVA having improved surface appearance. This is
effected by improving the fluidity of the DVA, relative to blends as
disclosed in U.S. Pat. No. 3,806,558, without degradation of the heat
resistance, tensile strength, flexibility, rebound-elasticity, etc.
U.S. Pat. No. 4,202,801 to Petersen relates to the partial dynamic curing
of a blend of a monoolefin copolymer rubber, such as saturated EPM or
EPDM; a polyolefin resin such as PP or PE, with a conjugated diene rubber
such as polybutadiene or polychloroprene. Crystalline polyolefin resin may
be used. The cure systems useful for the invention include the peroxides.
More than one monoolefin copolymer rubber, conjugated diene rubber and
polyolefin resin may be used in combination. The DVAs of this invention
are said to provide low compression set and high tensile strength at
elevated temperatures.
U.S. Pat. No. 4,340,684 to Bohm, et al. discloses a DVA composition which
is said to have very good physical properties, especially tear strength,
tensile strength, elongation at break, low temperature impact resistance,
minimum creep at high temperatures, and smooth surfaces when injection
molded. The compositions, which may be partially cured or uncured,
comprise a blend of from about 10 to about 50 wt. % of a crystalline
1-olefin polymer, from about 80 to about 15 wt. % of a styrene-butadiene
rubber, and from about 5 to about 55 wt. % of a highly saturated
elastomer. The 1-olefin polymer may be polypropylene. The highly saturated
elastomer is selected from the class consisting of hydrogenated
polybutadiene, polyisobutylene and copolymers thereof such as butyl
rubber, ethylene-propylene rubber (EPM), copolymers of ethylene-vinyl
acetate, copolymers of ethylene-ethylacrylate, ethylene-propylene-diene
monomer (EPDM), a hydrogenated "triblock copolymer of
styrene-butadiene-styrene" and combinations thereof.
U.S. Pat. No. 4,607,074 to Hazelton, et al. is directed to a thermoplastic
composition which comprises a polyolefin resin and two rubber components.
The first rubber component is selected from the group consisting of
polyisobutylene and ethylene-propylene copolymer and
ethylene-propylene-diene copolymer. The second rubber component is
selected from the group consisting of halogenated butyl rubber and
polychloroprene. The invention requires the use of a cure system which
vulcanizes one rubber but not the other. This results in a TPO having good
physical strength characteristics coupled with excellent processability,
low hardness and low compression set suitable for use in the manufacture
of molded and extruded articles such as gasketing materials, boot seals,
tubing, and the like.
U.S. Pat. No. 4,480,074 discloses DVA compositions said to exhibit improved
surface characteristics and fabricability wherein the compositions are
prepared by blending an unvulcanized, but vulcanizable, monoolefin rubber
with a blend containing cured polyolefin rubber with crystalline
polyolefin and subsequently vulcanizing such that the final blend
comprises about 15-45 parts by weight of crystalline polyolefin and 85-55
parts by weight of vulcanized rubber. EPDM is taught as both the
vulcanized polyolefin rubber and the unvulcanized but vulcanizable rubber
in the disclosed blends. Dynamic vulcanization utilizing peroxide cure
systems, phenolic resin systems, phenylene-bismaleimide and diamine
curatives, etc., is disclosed.
Japanese patent application 85,530/87 discloses a TPO composition having
excellent mechanical strength, thermal stability, moldability, gas
impermeability and damping characteristics. The TPO of the '530
application includes a crystalline polypropylene as a matrix and two
elastomers: a bromobutyl rubber and an olefin copolymer rubber such as EPM
or EPDM rubber. The composition also includes conventional additives such
as process oil. All of the components are combined and vulcanized in a
single batch with a peroxide cure system but there is no indication of the
inclusion of a peroxide co-agent such as m-phenylene bismaleimide (HVA-2)
or the like. The '530 application's inventors found that while butyl and
chlorobutyl rubbers are not cross-linkable with peroxide cures, bromobutyl
rubbers are. Moreover, the '530 application's inventors explain that the
enhanced physical properties claimed are due to the olefin copolymer
rubber which provides flexibility to the TPO and also acts as a binder at
the interface between the polypropylene and the bromobutyl rubber.
SUMMARY OF THE INVENTION
The DVAs of this invention have improved physical properties over prior art
two-rubber component blends. The inventive DVAs comprise a crystalline
polyolefinic resin and two vulcanized or co-vulcanized elastomers: a
primary butyl rubber-based elastomer, selected from butyl, chlorobutyl and
bromobutyl rubber, and one or more of a secondary EPM or EPDM elastomer.
In the process for the production of the invention DVA's:
(1) the elastomers may be simultaneously dynamically vulcanized using at
least two specific cure systems in a single mixing stage; or
(2) the elastomers may be dynamically vulcanized in a single mixing stage
using a cure system effective for both rubbers; or
(3) the elastomers may be dynamically vulcanized in a sequence by addition
of first a cure system for one rubber, then a cure system effective for
the other rubber or for both rubbers; or
(4) either elastomer may be independently dynamically vulcanized in a blend
with a crystalline polyolefinic phase and the resultant blend may then be
combined with the other elastomer, which may have been independently
dynamically vulcanized or which may be dynamically vulcanized
subsequently.
The final properties of these blends may be tailored by the selection of
the rubbers, cure systems, and mixing techniques.
Since butyl and chlorobutyl elastomers tend to fragment when exposed to a
peroxide-containing cure system, these cure systems are not recommended
for use with these elastomers. However, according to this invention,
peroxide-containing cure systems may advantageously be used to cure
bromobutyl elastomers in conjunction with a co-agent such as m-phenylene
bis maleimide (HVA-2) in processes for the production of improved DVA's.
DETAILED DESCRIPTION
This invention relates to the production of a dynamically vulcanized alloy
(DVA) of superior physical properties. The result of this invention is
achieved by mixing, in various fashions, a crystalline polyolefin resin
with two rubbers: a primary rubber selected from butyl rubber, chlorobutyl
rubber, and bromobutyl rubber; a secondary rubber selected from
ethylene-propylene rubber (EPM) and ethylene-propylene-diene rubber
(EPDM); and cure systems for both rubbers. These mixtures can then be
subjected to conditions of dynamic vulcanization, or melt blended where
both blends have been independently dynamically vulcanized, to produce the
invention DVA which has superior physical properties.
As used in the specification and claims, the term "dynamic vulcanization"
means a vulcanization process for a rubber-containing TPO composition
wherein the rubber is vulcanized under conditions of high shear, as a
result of which, the rubber is simultaneously cross-linked and dispersed
as fine particles of a "micro-gel" within the thermoplastic resin matrix.
Dynamic vulcanization is effected by mixing the TPO ingredients at a
temperature at or above the curing temperature of the rubber in equipment
such as roll mills, Banbury mixers, continuous mixers, kneaders or mixing
extruders, e.g., twin screw extruders. The unique characteristic of
dynamically cured compositions is that, notwithstanding the fact that the
rubber component is fully cured, the compositions can be processed and
reprocessed by conventional rubber processing techniques such as
extrusion, injection molding, compression molding, etc. Scrap or flashing
can be salvaged and reprocessed.
The term "dynamically vulcanized alloy" (DVA) as used in the specification
and claims means a composition comprising a crystalline polyolefin resin
containing at least one rubber wherein substantially all of the rubber has
been dynamically vulcanized to a fully cured state. The DVA compositions
are prepared by blending together the polyolefin resin and rubber with
cure systems and fillers under conditions of dynamic vulcanization.
The process for the production of the invention DVA is not restricted to
single-batch type operations, as described above, wherein the rubbers are
dynamically co-vulcanized with a cure system effective for both rubbers.
Other embodiments include a two-step process wherein first one rubber is
dynamically vulcanized to produce a dispersed micro-gel in the resin phase
and thereafter the second rubber, if not originally present, is added and
dynamically vulcanized. If both rubbers are initially present in the mix,
then the cure systems added sequentially should be distinct so that first
one and then the other rubber is vulcanized. If only one rubber is
initially present, then the same cure system may be used when the second
rubber is added, or a distinct cure system may be used to vulcanize the
second rubber.
In yet a further embodiment, the three batch process, the rubbers are each
individually dynamically vulcanized in separate blends which are then
combined and mixed to form the invention TPO.
Finally, as a variant of the single batch process, instead of adding a
single curing system effective for both rubbers, two distinct curing
systems may be added and the rubbers may then be simultaneously
dynamically vulcanized.
The term "rubber" as used in the specification and claims means any natural
or synthetic polymer which can be vulcanized or cured so as to exhibit
elastomeric properties.
The terms "primary" and "secondary" as used in relation to the rubbers of
this invention do not indicate the relative importance or proportions of
these rubbers in the blend but rather the terms are used as categories to
distinguish between the rubbers.
The terms "EPM" and "EPDM" are used in the sense of their ASTM
designations. EPM is an ethylene-propylene copolymer rubber which can be
cross-linked by radiation curing or peroxide curing. EPDM is a terpolymer
of ethylene, propylene and a non-conjugated diene. Illustrative
non-limiting examples of suitable non-conjugated dienes are
5-ethylidene-2-norbornene (ENB); 1,4-hexadiene ; 5-methylene-2-norbornene
(MNB); 1,6-octadiene; 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene;
1,3-cyclopentadiene; 1,4-cyclohexadiene; tetrahydroindene;
methyltetrahydroindene; dicyclopentadiene; 5-isopropylidene-2-norbornene;
5-vinyl-norbornene; etc.
Butyl rubber is a copolymer of an isoolefin and a conjugated multiolefin.
The useful rubber copolymers comprise a major portion of isoolefin and a
minor amount, preferably not more than 30 wt. %, of a conjugated
multiolefin. The preferred rubber copolymers comprise about 85-99.5 wt. %
(preferably 95-99.5 wt. %) of a C-C isoolefin, such as isobutylene, and
about 15-0.5 wt. % (preferably 5-0.5 wt. %) of a multiolefin of about 4-14
carbon atoms. These copolymers are referred to in the literature as "butyl
rubber"; see for example, the textbook Synthetic Rubber by G. S. Whitby
(1954 edition by John Wiley and Sons, Inc.) pp. 838-891. The term "butyl
rubber" as used in the specification and claims includes the
aforementioned copolymers of an isoolefin having 4-7 carbon atoms and
about 0.5 to 20 wt. % of a conjugated multiolefin of about 4-10 carbon
atoms. Preferably these copolymers contain about 0.5 to about 5%
conjugated multiolefin. The preferred isoolefin is isobutylene. Suitable
conjugated multiolefins include isoprene, butadiene, dimethyl butadiene,
piperylene, etc. Commercial butyl rubber is a copolymer of isobutylene and
minor amounts of isoprene.
The term "halogenated butyl rubber" as used in the specification and claims
refers to butyl rubber as described above which has been halogenated with
from about 0.1 to about 10, preferably, about 0.5 to about 3.0 wt. %
chlorine or bromine. The chlorinated species of butyl rubber is commonly
referred to as "chlorobutyl rubber" and the brominated species as
"bromobutyl rubber."
Additionally, one or more uncured rubbers may be used in the practice of
this invention. Illustrative, non-limiting examples of rubbers suitable
for use in the practice of this invention include butyl rubber,
halogenated butyl rubber, ethylene-propylene rubber (EPM),
ethylene-propylene-diene rubber (EPDM), polyisoprene, polychloroprene,
styrene-butadiene rubber, polybutene copolymers, nitrile rubbers,
chloro-sulfonated polyethylene, etc. and mixtures thereof. While
polyisobutylene is not a true rubber because it cannot be vulcanized, it
can be utilized in the practice of this invention provided that it has a
viscosity average molecular weight of from about 40,000 to about 1
million.
The preferred polyolefin resins are high density polyethylene (HDPE) and
polypropylene. While other polyolefin homopolymers and copolymers of
ethylene can be utilized in the practice of this invention, the resulting
DVA compositions are deficient in high temperature characteristics. Such
other polyolefins include low density polyethylene (LDPE), linear low
density polyethylene (LLDPE) and polybutylene (PB), as well as copolymers
of ethylene with vinyl acetate, acrylic acid, methyl acrylate, ethyl
acrylate, ethylene-1 olefin copolymers (such as ethylene-butene and
ethylene-hexene), etc. However, these other polyolefin resins can be
incorporated into the DVA compositions of this invention along with the
polypropylene ("PP") or polyethylene ("PE"). As used in the specification
and claims, the term "polypropylene" includes homopolymers of propylene as
well as reactor copolymers of polypropylene (RCPP) which can contain about
1 to about 20 wt. % ethylene or an alpha olefin comonomer of 4 to 16
carbon atoms, and mixtures thereof. The polypropylene can be highly
crystalline isotactic or syndiotactic polypropylene. The RCPP can be
either a random or block copolymer. The density of the PP or RCPP can be
about 0.80 to about 0.9 g/cc; generally, about 0.89 to about 0.91 g/cc.
High density polyethylene (HDPE), useful as the polyolefin resin of this
invention, has a density of about 0.941 to about 0.965 g/cc. High density
polyethylene is an established product of commerce and its manufacture and
general properties are well known to the art. Typically, HDPE has a
relatively broad molecular weight distribution, characterized by the ratio
of weight average molecular weight to number average molecular weight of
from about 20 to about 40.
Polyolefin resins which can optionally be included in the compositions of
this invention include polybutylene, LDPE and LLDPE as well as copolymers
of ethylene with unsaturated esters of lower carboxylic acids. The term
"polybutylene" generally refers to thermoplastic resins of both
poly(1-butene)homopolymer and the copolymer with, for example, ethylene,
propylene, pentene-1, etc. Polybutylene is manufactured via a
stereo-specific Ziegler-Natta polymerization of monomer(s). Commercially
useful products are of high molecular weight and isotacticity. A variety
of commercial grades of both homopolymer and ethylene copolymer are
available with melt indices that range from about 0.3 to about 20 g/10
min.
The term "low density polyethylene" or "LDPE" as used in the specification
and claims mean both low and medium density polyethylene having densities
of about 0.910 to about 0.940 g/cc. The terms include linear polyethylene
as well as copolymers of ethylene which are thermoplastic resins.
Linear low density polyethylene (LLDPE) is a class of low density
polyethylene characterized by little, if any, long chain branching, in
contrast to conventional LDPE. The processes for producing LLDPE are well
known in the art and commercial grades of this polyolefin resin are
available. Generally, it is produced in gas-phase fluidized bed reactors
or liquid-phase solution process reactors; the former process can be
carried out at pressures of about 100 to 300 psi and temperatures as low
as 100.degree. C.
The invention DVA includes compositions wherein the primary elastomer
ranges from about 10 to about 90 wt. %, preferably about 15 to 85 wt. %
and most preferably about 40 to 60 wt. % based upon the total weight of
the elastomers.
The weight percent of the secondary elastomer may vary from about 90 to
about 10 wt. %, preferably about 85 to 15 wt. % and most preferably about
60 to 40 wt. % based upon the weight of the elastomers.
The crystalline polyolefin content of the DVA may vary from about 10 wt. %
to about 90 wt. % based upon the total weight of the elastomers and the
crystalline polyolefin. However, it is preferred that the crystalline
polyolefin content range from about 15 to 60 wt. %, most preferably from
about 30 to 40 wt. % based upon the total weight of the elastomers and the
crystalline polyolefin.
In addition to its polymer component, the DVA composition of this invention
can include reinforcing and non-reinforcing fillers, antioxidants,
stabilizers, rubber processing oils, lubricants (e.g., oleamide),
antiblocking agents, antistatic agents, waxes, coupling agents for the
fillers, foaming agents, pigments, flame retardants, and other processing
aids known to the rubber compounding art. The pigments and fillers can
comprise up to 50 wt. % of the total DVA composition based on polymer
component plus additives; preferably pigments and fillers comprise about 0
to about 30 wt. % of the total composition.
Fillers can be inorganic fillers such as calcium carbonate, clays, silica,
talc, titanium dioxide or carbon black. Any type of carbon black can be
used, such as channel blacks, furnace blacks, thermal blacks, acetylene
black, lamp black and the like.
Rubber process oils have particular ASTM designations depending on whether
they fall into the class of paraffinic, naphthenic or aromatic process
oils. They are derived from petroleum fractions. The type of process oil
utilized will be that customarily used in conjunction with the rubber
component. The ordinarily skilled rubber chemist will recognize which type
of oil should be utilized with a particular rubber. The quantity of rubber
process oil utilized is based on the total rubber content, both cured and
uncured, and can be defined as the ratio, by weight, of process oil to the
total rubber in the DVA. This ratio can vary from about 0 to about 1.5/1;
preferably about 0.2/1 to about 1.00/1; more preferably about 0.3/1 to
about 0.8/1. Larger amounts of process oil can be used, the resultant
effect being reduced physical strength of the composition. Oils other than
petroleum based oils, such as oils derived from coal tar and pine tar, can
also be utilized. In addition to the petroleum derived rubber process
oils, organic esters and other synthetic plasticizers can be used.
Antioxidants can be utilized in the composition of this invention--the
particular antioxidant utilized will depend on the rubbers utilized and
more than one type may be required. Their proper selection is well within
the ordinary skill of the rubber processing chemist. Antioxidants will
generally fall into the class of chemical protectors or physical
protectors.
Physical protectors are used where there is to be little movement in the
part to be manufactured from the composition. The physical antioxidants
include mixed petroleum waxes and microcrystalline waxes. These generally
waxy materials impart a "bloom" to the surface of the rubber part and form
a protective coating to shield the part from oxygen, ozone, etc.
The chemical protectors generally fall into three chemical groups;
secondary amines, phenolics and phosphites. Illustrative, non-limiting
examples of types of antioxidants useful in the practice of this invention
are hindered phenols, amino phenols, hydroquinones, alkyldiamines, amine
condensation products, etc. Further non-limiting examples of these and
other types of antioxidants are styrenated phenol; 2, 2'-methylene-bis
(4-methyl-6-t-butylphenol); 2,6'-di-t-butyl-o-dimethylamino-p-cresol;
hydroquinone monobenzyl ether; octylated diphenyl amine;
phenyl-beta-naphthylamine; N,N'-diphenylethylene diamine;
aldol-alpha-naphthylamine; N,N'-diphenyl-p-phenylene diamine; etc.
Any conventional cure system for the rubber to be dynamically vulcanized
can be used. These include sulfur cures as well as non-sulfur cures. For
example, halogenated butyl rubber can be cured using zinc oxide. Of
course, accelerators such as dithiocarbamates or thiurams and thioureas
can be included in these zinc oxide cures. Zinc oxide free cures of
halogenated butyl rubber known to the art can also be utilized. For
example, such cure systems comprise litharge, 2-mercaptoimidazoline and
diphenyl guanidine.
Resin cure systems can be used for butyl rubber, halogenated butyl rubber
and the EPDM rubbers. The resins useful in cure systems are phenolic
resins, brominated phenolic resins, urethane resins, etc. The halogenated
resin cure systems are generally metal activated where the rubber is butyl
rubber or an EPDM.
While phenolic resin cures are suitable cures, they impart a yellowish or
orangish tinge to the rubber part. For halogenated butyl rubber, a
preferred cure system is one based on ZnO and MgO. Such cure systems
permit the use of pigments such as TiO to give bright white compositions.
In this system, the MgO acts not as an accelerator but as an acid acceptor
to stabilize the rubber from dehydrohalogenation.
Organic peroxides may be used in the cure systems of the invention DVA
except where the primary elastomer is butyl or chlorobutyl rubber, and
preferred cure systems include peroxides where bromobutyl rubber is the
primary elastomer. Specific examples of the useful organic peroxides are
octanoyl peroxide, lauroyl peroxide, benzoyl peroxide, tert-butyl
peroctoate, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide,
cyclohexanone peroxide, tert-butyl peroxybenzoate, methyl ethyl ketone
peroxide, dicumyl peroxide, di-tert-butyl peroxide,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl
diperoxyphthalate, tert-butylcumyl peroxide, diisopropylbenzene
hydroperoxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, tert-butyl
peroxypivalate, 3,5,5-trimethylhexanoyl peroxide,
1,1-bis(tert-butylperoxy)-3,5,5-trimethylcyclohexane,
1,1-bis(tert-butylperoxy)cyclohexane, etc.; azo compounds such as
azobisisbutyronitrile, etc.; and the like.
The peroxide-based cure systems may be used with or without co-agents such
as sulfur, ethylene dimethacrylate, polyethylene glycol dimethacrylate,
trimethylol propane trimethacrylate, divinyl benzene, diallyl itaconate,
triallyl cyanurate, diallyl phthalate, allyl methacrylate, cyclohexyl
methacrylate, m-phenylene bis maleimide (HVA-2), and the like.
When used to cure bromobutyl rubber in accordance with this invention, the
peroxide-based cure systems should preferably be utilized with a co-agent
or co-agents capable of enhancing the cure-state and inhibiting chain
fragmentation or scission effects. Examples of such include specifically
known maleimide compounds used as co-agent. The maleimide compound
preferably used in the invention is a bismaleimide compound. Among the
maleimide compounds, a bismaleimide compound is especially superior in
effectiveness and m-phenylene bismaleimide (4,4'-m-phenylene bismaleimide)
is preferred. Examples of the bismaleimide are 4,4'-vinylenediphenyl
bismaleimide, p-phenylene bismaleimide, 4,4'-sulfonyldiphenyl
bismaleimide, 2,2'-dithiodiphenyl bismaleimide,
4,4'-ethylene-bis-oxophenyl bismaleimide, 3'3-dichloro-4, 4'-biphenyl
bismaleimide, o-phenylene bismaleimide, m-phenylene bismaleimide (HVA-2),
hexamethylene bismaleimide and 3,6-durine bismaleimides. The maleimide
compound will generally be used in an amount equal to about 1.0 to 10
parts per hundred parts of curable elastomer cured with either peroxide or
non-peroxide curing systems. This range takes into account the use of
certain maleimide compounds as co-agents or both peroxide cure systems and
ZnO based cure systems when both are used.
Illustrative of accelerators which can be used in conjunction with ZnO for
curing halobutyl rubber are 2,6-di-tert-butyl-para-cresol;
N,N'-diethylthiourea; di-ortho-tolylguanidine; dipentamethylene thuiram
tetrasulfide; ethylene trithiocarbonate; 2-mercapto-benzothiazole;
benzothiazole disulfide; N-phenyl-beta-naphthylamine; tetramethyl thuiram
disulfide, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and
zinc dimethyldithiocarbamate. Formulations for the ZnO cure of halobutyl
rubber are well known in the art. A preferred cure system comprises ZnO
and m-phenylene bismaleimide since this system results in a vulcanized
rubber with low compression set.
In the practice of this invention an uncured crystalline polyolefin resin
is mixed with a halogenated butyl rubber and an EPM or EPDM rubber at a
temperature sufficient to soften the resin or, more commonly, where the
resin is crystalline at room temperature, to a temperature above its
melting point. After the resin and rubbers are intimately mixed, the cure
system is added. When chlorobutyl or butyl rubber forms part of the
elastomeric component, a non-peroxide cure system should be used for
curing the butyl or chlorobutyl rubber.
Peroxide cure systems may be effectively used to cure bromobutyl
rubber-containing compositions, particularly when used with a maleimide
compound as a co-agent. However, the use of peroxide curing systems is
known to create problems for polyolefin resins. For example, polypropylene
will undergo chain fragmentation or scission to some extent and
polyethylene will tend also to undergo cross-linking reactions. Chain
fragmentation or scission can be effectively suppressed by utilization of
agents which accelerate the vulcanization of the rubber, for example the
peroxide co-agents described above. Also suppression can be achieved by
delaying the introduction of some part or portion of the polyolefin resin,
generally less than about one half the total amount of polyolefin resin
used. To best avoid excessive cross-linking of the polyolefin resin, it
will comprise a significant portion of a polypropylene homo- or copolymer.
By "significant portion" it is meant that at least about 12 wt. %
polypropylene based upon the total weight of resin plus rubber is present.
Thus where a peroxide curing system is utilized, the polyolefin resin will
preferably be polypropylene or a mix of polypropylene with other olefin
based resins.
Heating and masticating at vulcanization temperatures are generally
adequate to complete vulcanization in about 0.5 to about 10 minutes. The
vulcanization time can be reduced by elevating the temperature of
vulcanization. A suitable range of vulcanization temperatures is from
about the peak melting point of the resin (about 160.degree. to
165.degree. C. in the case of polypropylene) to about 250.degree. C.; more
typically, the temperature range is about 150.degree. C. to about
230.degree. C. Preferably the vulcanization is carried out at a
temperature of about 180.degree. C. to about 220.degree. C.
It is preferred that the mixing process be continued until the
vulcanization reactions are complete. If vulcanization reactions are
permitted to continue after mixing has stopped, the composition will not
be reprocessible as a thermoplastic. However, the dynamic vulcanization
can be carried out in stages. For example, by the addition of a cure
system specific to one of the elastomers during melt processing but after
the vulcanization of the other elastomer. In another example,
vulcanization can be commenced at high temperatures in a twin screw
extruder and before vulcanization is complete pellets can be formed of the
partially prepared DVA using an underwater pelletizer thereby quenching
the curing step. At a later time vulcanization can be completed under
dynamic vulcanization conditions, for example, a second curing system can
be added to the pellets which can be subsequently melt processed.
Furthermore, either elastomer may be independently dynamically vulcanized
in a blend with a crystalline polyolefinic phase and the resultant blend
may then be combined with the other elastomer, which may have been
independently dynamically vulcanized or which may be dynamically
vulcanized subsequently.
Those ordinarily skilled in the art will appreciate the appropriate
quantities, types of cure systems and extent of mixing time required to
carry out the vulcanization of the rubber. Where necessary the rubber can
be vulcanized using varying amounts of cure system to determine the
optimum cure system to be utilized and the appropriate cure conditions to
obtain a full cure.
The term "fully vulcanized" as used in the specifications and claims with
respect to the dynamically vulcanized rubber component of this invention
means that the rubber component to be vulcanized has been cured to a state
in which the elastomeric properties of the rubber are similar to those of
the rubber in its conventional vulcanized state. The degree of cure of the
vulcanized rubber can be described in terms of gel content or, conversely,
extractable components. Alternatively, the degree of cure can be expressed
in terms of cross-link density.
Where the determination of extractables is an appropriate measure of the
state of cure, the improved thermoplastic elastomeric compositions are
produced by vulcanizing the curable rubber component of the blends to the
point where the composition contains no more than about four percent by
weight of the cured rubber component extractable at room temperature by a
solvent which dissolves the rubber which is intended to be vulcanized. The
rubbers are preferably vulcanized to the point that the composition
contains less than two percent by weight of extractables. In general, the
less extractables in the cured rubber component, the better are the
properties. Still more preferable are compositions comprising essentially
no extractable rubber from the cured rubber phase (less than 0.5 wt. %).
Gel content reported as percent gel is determined by a procedure which
comprises determining the amount of insoluble polymer by soaking the
specimen for 48 hours in organic solvent at room temperature and then
weighing the dried residue and making suitable corrections based upon
knowledge of the composition. Thus, corrected initial and final weights
are obtained by subtracting from the initial weight, the weight of soluble
components, other than the rubber to be vulcanized, such as extender oils,
plasticizers and components of the compositions soluble in organic
solvent, as well as that rubber component of the DVA which it is not
intended to cure. Any insoluble pigments, fillers, etc., are subtracted
from both the initial and final weights.
To employ cross-link density as the measure of the state of cure which
characterizes the improved thermoplastic elastomeric compositions, the
blends are vulcanized to the extent which corresponds to vulcanizing the
same rubber as in the blend statically under pressure in a mold with such
amounts of the same cure systems as in the blend and under such conditions
of time and temperature to give an effective cross-link density greater
than about 3.times.10 moles per milliliter of rubber and preferably
greater than about 5.times.10, or even more preferably, 1.times.10 moles
per milliliter of rubber. The blend is then dynamically vulcanized under
similar conditions with the same amount of cure system based on the rubber
content of the blend as was required for the rubber alone. The cross-link
density so determined may be regarded as a measure of the amount of
vulcanization which produces the improved thermoplastics. However, it
should not be assumed, from the fact that the amount of cure system is
based on the rubber content of the blend and is that amount which gives
the rubber alone the aforesaid cross-link density, that the cure system
does not react with the resin or that there is no reaction between the
resin and rubber. Highly significant reactions of limited extent may be
involved. However, the assumption that the cross-link density determined
as described provides a useful approximation of the cross-link density of
the thermoplastic elastomeric compositions is consistent with the
thermoplastic properties and with the fact that the large proportion of
the resin can be removed from the composition by high temperature solvent
extraction, for example, by boiling decalin extraction.
The cross-link density of the rubber is determined by equilibrium solvent
swelling using the Flory-Rehner equation. J. Rubber Chem. and Tech. 30, p.
929. The appropriate Huggins solubility parameters for rubber-solvent
pairs used in the calculation were obtained from the review article by
Sheehan and Bisio, J. Rubber Chem. & Tech., 39, 149. If the extracted gel
content of the vulcanized rubber is low, it is necessary to use the
correction of Bueche wherein the term "v" is multiplied by the gel
fraction (% gel/100). The cross-link density is half the effective network
chain density "v" determined in the absence of resin. The cross-link
density of the vulcanized blends should therefore be understood to refer
to the value determined on the same rubber as in the blend in the manner
described. Still more preferred compositions meet both of the
aforedescribed measures of state of cure, namely, by estimation of
cross-link density and percent of rubber extractable.
The following examples serve to illustrate the process and product
properties of the instant invention and are not intended to limit the
scope of this invention.
EXAMPLE A
Two control DVA formulations were produced, one having only EPDM as the
elastomer, sample 1, the other having bromobutyl rubber, sample 2. The
compositions of these DVA-formulations are shown in Table IA and their
physical properties in Table I. (Note that of the weight percent VISTALON
3777 used in Examples A, B, C, D and E 57 wt. % is EPDM and the remainder
is oil. Thus, for instance, sample 1 effectively contains 28.5 wt. % EPDM
and samples 3, 4, 5 and 6 contain 14.25 wt. % EPDM).
Sample 1 was prepared by mixing together all components, except the cure
system and about one-half of the oil (not all oil was added so as to
decrease mixing time) for about 4 minutes in a Banbury mixer while the
temperature was increased to about 180.degree. C. At that stage, the cure
system was added while mixing continued. After a total of about 8 minutes
had elapsed, the remainder of the oil was added while mixing. Two minutes
later, the product was discharged from the Banbury, then sheeted out on an
open mill and ground up for charge to an injection molding machine.
Dumbbells were molded and their properties measured.
The bromobutyl blend formulation, sample 2, was prepared by a similar
method. Dumbbells were made and tested.
The composition of invention samples 3, 4, 5, and 6 are also shown in Table
IA.
In sample 3 the EPDM was cured first in the composition of sample 1.
Thereafter the bromobutyl rubber and the remaining ingredients were added
with the bromobutyl being subsequently cured to produce the final sample 3
DVA. The results of physical property tests on dumbbells of this DVA and
those of samples 4, 5 and 6 are shown in Table I. The test procedures in
measuring the physical properties of sample 3 and all the other samples,
both control and invention, are identified in Table VIII.
In sample 4 the bromobutyl rubber was cured first in the composition of
sample 2 and the EPDM and remaining ingredients added and cured second to
produce a DVA product which was then tested.
In sample 5 the two rubbers were cured together and the DVA product tested.
In sample 6 the bromobutyl rubber and the EPDM rubber were each cured
separately under conditions of dynamic vulcanization in blends which were
then combined during melt processing to produce a DVA product which was
tested.
The "control" samples serve as both controls representing commercial
formulations such as, for instance, those of U.S. Pat. Nos. 4,130,535 and
4,311,628 to Monsanto, and also as base compositions from which invention
compositions may be produced.
In all four invention samples, the tensile strength exceeded that of the
bromobutyl-based sample 2 while being either comparable to that of the
EPDM-based sample 1 or well within useful limitations thereof. Moreover,
the invention samples' resistance to heat aging exceeded that of the
EPDM-based control, sample 1.
EXAMPLE B
A series of tests similar to Example A were carried out using variations of
formulations containing EPDM and chlorobutyl rubber with individual EPDM
and chlorobutyl rubber containing blends as the control formulations, 1
and 7. The blend compositions are shown in Table IIA and the results of
physical property tests on dumbbells of the DVA products are shown in
Table II.
The results of this series of tests are similar to that of Example A.
EXAMPLE C
Blend formulations were produced at varying levels of bromobutyl rubber
content using the method of sample 3. The compositions of these blends and
test results on the DVA products are summarized in Table III. Sample 12
contained no bromobutyl rubber and provided an EPDM-based control DVA.
Samples 13-15 contained from about a 60:40 to about a 85:15 ratio of
bromobutyl to EPDM rubber.
The invention formulations containing a combination of bromobutyl and EPDM
rubbers show benefits over the EPDM control. The tensile strength of the
normally weaker butyl-based DVAs has increased to a level equal to or
greater than that of the EPDM-based control DVA. Moreover, heat resistance
of the invention DVAs are superior to that of the control and show useful
levels of tensile strength and elongation even after 60 days at
150.degree. C. in samples 14 and 15.
EXAMPLE D
Blend formulations with varying ratios of bromobutyl: EPDM rubber were
tested in an experiment parallel to that of Example C but using a
sulfur/sulfur donor cure system to cure the EPDM. The blend compositions
and DVA product test results are shown in Table IV.
From the test results in Tables I and IV, it is apparent that use of a low
sulfur/sulfur donor cure system for EPDM (sample 16) in place of a resin
cure system (sample 1) results in lowered tensile strength in the all
EPDM-based control. However, excellent synergistic results are obtained in
the sulfur-cured invention formulations, samples 17, 18 and 19.
EXAMPLE E
In this series of blends, shown in Table V, the properties of the
EPDM/bromobutyl rubber-based invention DVAs (samples 21, 22) are compared
with two control DVAs. In one control DVA only bromobutyl rubber is used
as the elastomeric phase (sample 20) while in the other a preformed EPDM
composition which is not cured is added to the bromobutyl-based blend
(sample 23). One of the invention DVAs, sample 22, includes a
commercially-available EPDM DVA composition sold under the trade name
SANTOPRENE.
The data for sample 21 confirms a previous result shown in Example C,
namely that even a small amount of a compound containing dynamically
vulcanized EPDM, when included in a dynamic vulcanizate containing a large
amount of bromobutyl rubber, produces a product with improved tensile
strength and excellent heat aging. Here the comparison is between sample
21, which is a DVA as described in sample 15 in Example C and sample 20, a
control using only bromobutyl elastomer which is a DVA as described in
sample 2 in Example A. In sample 22, the preformed EPDM dynamic
vulcanizate was a commercial product, SANTOPRENE 201-73. SANTOPRENE 201-73
is believed to be very similar in composition to the EPDM composition
shown in Table IA as sample 1 which was used to make sample 21, so the
final composition may be expected to be similar and results are almost
identical.
The control, sample 23, was made in the same manner as sample 21 except
that the EPDM composition used as a starting ingredient was pre-mixed and
not cured (it was like sample 1 in Examples A and B, but an additional 4.8
parts of the inert clay were substituted for the zinc oxide and SP 1056
curatives). There is some improvement relative to sample 20 but tensile,
elongation and tear are below those of the claimed inventive compounds.
Note that the composition of control compound sample 23 is taught in U.S.
Pat. No. 4,607,074.
EXAMPLE F
Inventive compositions as described in Table VI were dynamically vulcanized
in a Banbury mixer. In Sample 24 and sample 25, the rubbers were
co-vulcanized with the addition of a single cure system. In Sample 24 the
rubbers and PP COPOLYMER 7824 were mixed together with all the additives
except for the cure system, wax and oil for about 6.5 minutes during which
time the temperature was increased to about 180.degree. C. During this
mixing and heating time, the oil was added in three portions. At the end
of this time, the SP 1056/SnCl.sub.2 H.sub.2 O/ZnO cure system was added
while mixing continued. After a total mixing time of about 13.5 minutes
had elapsed, the wax was added while mixing. After about one minute, the
blend was sheeted out onto an open mill and ground for charge to an
injection molding machine. Dumbbells were injection molded from each of
the blends and their properties were compared.
DVA sample 25 was prepared as above except that NEUTRAL 600 oil was used in
the blend as an additive instead of SUNPAR 2280.
In preparing the blend of sample 26, the polymer, rubber and additives were
mixed for about 11 minutes while heating to over 170.degree. C. before the
cure system co-agent HVA-2 was added. About one minute later, the ZnO was
added and about 4 minutes thereafter, the SP 1056/SnCl.sub.2 H.sub.2 O was
added. After about 6 minutes when dynamic vulcanization was complete, the
wax was added and one minute later the blend was sheeted out onto an open
mill.
In preparing the blend of sample 27, the polymer, rubber and additives were
blended as for sample 26 except that the HVA-2 was added after about 10.5
minutes of mixing, the ZnO about one minute later, the resin and SP
1056/SnCl.sub.2 H.sub.2 O four minutes later and the wax 3 minutes
thereafter. After a further one minute of mixing, the blend was sheeted
out onto an open mill.
Comparative samples 28, 29 and 30 are commercially available DVAs which the
inventors believe are EPDM-based and which are sold by MONSANTO CHEMICAL
COMPANY (St. Louis, Mo.) under the trade names SANTOPRENE 201-64,
SANTOPRENE 201-73 and SANTOPRENE 201-80, respectively.
Comparing samples 24 and 25, it is apparent that a change in the type of
oil used has some effect and that the NEUTRAL 600-containing DVA (sample
25) has a somewhat reduced percentage elongation and tensile strength as
compared to the SUNPAR-containing DVA (sample 24).
A comparison of the invention blends, 24, 25, 26, and 27 with the
commercially available DVAs of samples 28, 29 and 30 shows the superiority
of the invention DVAs' tensile strength.
EXAMPLE G
DVA samples were prepared in a Banbury mixer using peroxide as part of the
cure system. The composition and properties of these DVAs are shown in
Table VII.
In sample 31, the rubbers and polypropylene were mixed together with all
additives (except antioxidants, cure system and wax) for about 5 minutes
at 180.degree. C. Oil was added in 3 portions during these 5 minutes of
mixing. At this stage, the entire cure system was added while mixing
continued. After a total mixing time of about 14 minutes, wax and
antioxidants were added, while mixing continued. About 2 minutes later,
the sample was sheeted out onto an open mill and ground up for charge into
an injection-molding machine. Samples were die cut from injection-molded
plates for physical property measurements.
Sample 32 was prepared in the same way as sample 31, except that ZnO/HVA-2
were added first after about 6 minutes of mixing at 180.degree. C., then
about 1 minute later, after at least partial curing of the bromobutyl
rubber, peroxide was added.
Sample 33 was prepared in the same way as sample 31, except that the ZnO
and one-third of the HVA-2 were added after about 6 minutes of mixing at
180.degree. C. After about 12 minutes of mixing, when the bromobutyl
rubber was fully cured, the sample was sheeted out onto an open mill then
ground up. This sample was tumbled with two-thirds of the HVA-2 and
peroxide and then remixed in a Banbury mixer at 180.degree. C. for about 9
minutes. Wax and antioxidants were added during the remix, 2 minutes
before dumping.
Sample 34 was produced using an EPDM, VISTALON 3666 as the cured rubber,
while sample 35 contained bromobutyl 2244 as the cured rubber.
Sample 34 was produced by mixing polymers and additives including HVA-2,
for about 9 minutes at 180.degree. C. during which time the oil was added
in 2 portions. At this stage, peroxide was added and the EPDM rubber was
dynamically vulcanized. After a total mixing time of about 17 minutes, wax
and antioxidants were added and 2 minutes later sample was dumped, sheeted
out and ground up for test sample production.
Sample 35 was produced by mixing polymers and additives for about 9 minutes
at 180.degree. C. during which time the oil was added in 3 portions. At
this stage, HVA-2/ZnO was added and the bromobutyl rubber was dynamically
vulcanized. After a total mixing time of about 20 minutes, wax and
antioxidants were added and 2 minutes later sample was dumped, sheeted out
and ground up for test sample production.
Sample 37 was produced in the same way as sample 35, except that sample 37
contained 5% uncured VISTALON 808.
Samples 36 and 38 were prepared by the three-blend embodiment of the
present invention. Two individual dynamically vulcanized blends were
produced which were then blended during melt processing into a single
dynamically vulcanized blend.
Sample 36 was produced by mixing samples 34 and 35 in a 50/50 proportion at
180.degree. C. for about 6 minutes.
Sample 38 was produced by mixing samples 34 and 37 in a 50/50 proportion at
180.degree. C. for about 6 minutes.
The difference in properties between samples 31-33 illustrate the effect of
their production processes. Sample 31, having the lowest tensile strength
and percentage elongation of the trio, was prepared in a single batch
operation wherein the elastomers were all cured together by the one-step
addition of the cure system. Sample 32, the DVA having intermediate
percentage elongation and tensile strength, was prepared by first
partially curing the bromobutyl rubber before adding the peroxide cure.
Finally, sample 33, the DVA with the best percentage elongation and
tensile strength was prepared by first fully curing the bromobutyl rubber
before adding the peroxide cure.
Samples 34-38 illustrate the superiority of the invention DVAs which
contain both a bromobutyl rubber and an EPDM rubber over the prior art
DVAs which contain only one of these rubbers. Thus, for instance, sample
36 which is an invention blend, has superior tensile strength and
percentage elongation with respect to its component single-rubber DVAs,
samples 34 and 35. Similarly, invention DVA sample 38 has superior
percentage elongation and tensile strength to samples 34 and 37.
TABLE I
__________________________________________________________________________
Dynamically Vulcanized Bromobutyl/EPDM Formulations
INVENTION
Formulations Combining Bromobutyl and EPDM
CONTROLS EPDM Bromobutyl
Cured
Cured Separately
EPDM
Bromobutyl
Cured 1st
Cured 1st
Together
Blended
Compound 1 2 3 4 5 6
__________________________________________________________________________
FLOW PROPERTIES
Spiral Flow, cm 15 16.5 19 17 18 16.5
MFR @ 230.degree. C., 10 Kg
0.5
31 2 16 14 14
PHYSICAL PROPERTIES
Injection Molded,
Die Cut Dumbbells:
Hardness, Shore A, 10 sec.
68 69 68 69 67 64
100% Modulus, psi
520 480 490 440 480 450
Tensile Strength, psi
1130
900 1160 990 1000 1100
Elongation, % 410 280 350 380 300 380
Tear Strength, Die B, pli
230 220 220 220 220 213
THERMAL STABILITY
Compression Set B, %
22 Hr. @ 100.degree. C.
46 40 41 51 50 45
22 Hr. @ 150.degree. C.
70 68 69 not tested
not tested
70
High Temperature Aging:
Air Oven Aging, 14 days @ 150.degree. C.
Hardness Change, Points
+3 +1 +2 +1 0 +6
% Tensile Retained
76 107 108 118 138 111
% Elongation Retained
59 93 83 88 112 73
Air Oven Aging, 30 days @ 150.degree. C.
Hardness Change, Points
+9 -3 -1 -1 -4 0
% Tensile Retained
18 98 83 102 102 81
% Elongation Retained
Brittle
75 60 72 91 56
ASTM #3 Oil, 70 Hr. @ 100.degree. C.
Volume Swell, % 83 77 82 105 102 88
PROPORTIONS 0:100
100:0 59.5:40.5
59.5:40.5
59.5:40.5
59.5:40.5
Ratio of Bromobutyl to EPDM
__________________________________________________________________________
TABLE IA
__________________________________________________________________________
CONTROLS INVENTION
EPDM Formulation, 1 Bromobutyl Formulation, 2
Formulations 3, 4, 5, 6, with Two
Elastomers
__________________________________________________________________________
Vistalon 3777 (EPDM: Oil 57:43)
50.0
Bromobutyl 2244
42.0
Vistalon 3777 25.0
Sunolite 127 Wax
1.5 Maglite D 0.5 Bromobutyl 2244 21.0
PP 5052 16.7
PP 5052 18.0
Maglite D Magnesium Oxide
0.3
Nucap 190 Clay 8.2 Nucap 190 Clay
3.5 PP 5052 Polypropylene
17.35
Titanox 2071 1.0 Titanox 2071
3.0 Nucap 190 Clay 5.8
Stearic Acid 0.5 Stearic Acid
0.5 Titanox 2071 2.0
Sunpar 150 Oil 16.0
Sunpar 150 Oil
28.0
Sunolite 127 Wax
0.75
Irganox 3114 0.5 Vanox MTI 0.5 Stearic Acid 0.45
Ultranox 626 0.8 Protox 169 ZnO
3.0 Sunpar 150 Oil 22.0
Protox 169 ZnO 0.8 HVA-2 1.0 Vanox MTI 0.3
SP 1056 Resin 4.0 Irganox 3114 0.25
Protox 169 Zinc Oxide
1.9
SP 1056 Resin 2.0
HVA-2 0.5
100.00 100.00 100.00
__________________________________________________________________________
TABLE II
__________________________________________________________________________
Dynamically Vulcanized Chlorobutyl/EPDM Formulations
INVENTION
CONTROL Formulations Combining Chlorobutyl and EPDM
Formulations
EPDM Chlorobutyl
Cured
Cured Separately
EPDM
Chlorobutyl
Cured 1st
Cured 1st
Together
Blended
1 7 8 9 10 11
__________________________________________________________________________
FLOW PROPERTIES
Spiral Flow, cm 15 15.5 15.5
19.5 15.5
14
MFR @ 230.degree. C., 10 Kg
0.5
8.9 1.4
2.6 1.1
0.9
PHYSICAL PROPERTIES
Injection Molded,
Die Cut Dumbbells:
Hardness, Shore A, 10 sec.
68 67 67 69 69 62
100% Modulus, psi
520 480 480 470 480 460
Tensile Strength, psi
1130
960 1010 1000 1000 1100
Elongation, % 410 300 330 380 360 420
Tear Strength, Die B, pli
230 210 200 210 210 210
THERMAL STABILITY
Compression Set B, %
22 Hr. @ 100.degree. C.
46 42 48 58 52 57
22 Hr. @ 150.degree. C.
70 59 65 not tested
not tested
not tested
High Temperature Aging:
Air Oven Aging, 14 days @ 150.degree. C.
Hardness Change, Points
+3 0 0 +1 -2 +6
% Tensile Retained
76 77 98 99 95 84
% Elongation Retained
59 71 57 64 62 46
Air Oven Aging, 30 days @ 150.degree. C.
Hardness Change, Points
+9 -2 0 -1 -1 +4
% Tensile Retained
18 69 56 64 68 57
% Elongation Retained
Brittle
47 32 33 43 30
ASTM #3 Oil, 70 Hr. @ 100.degree. C.
83 102 96 124 103 109
Volume Swell, %
PROPORTIONS 0:100
100:0 59.5:40.5
59.5:40.5
59.5:40.5
59.5:40.5
Ratio of Chlorobutyl to EPDM
__________________________________________________________________________
TABLE IIA
__________________________________________________________________________
CONTROL FORMULATIONS INVENTION
EPDM Formulation, 1 Chlorobutyl Formulation, 7
Formulations 8, 9, 10, 11, with Two
Elastomers
__________________________________________________________________________
Vistalon 3777 (EPDM: Oil 57:43)
50.0
Chlorobutyl 1068
42.0
Vistalon 3777 25.0
Sunolite 127 Wax
1.5 Maglite D 0.5 Chlorobutyl 1068
21.0
PP 5052 16.7
PP 5052 19.0
Maglite D 0.3
Nucap 190 Clay 8.2 Titanox 2071
3.2 Sunolite 127 Wax
0.7
Titanox 2071 1.0 Stearic Acid
0.5 PP 5052 17.9
Stearic Acid 0.5 Sunpar 150 Oil
27.0
Nucap 190 Clay
4.1
Sunpar 150 Oil 16.0
Irganox 3114
0.5 Titanox 2071 2.0
Irganox 3114 0.5 Ultranox 626
0.8 Stearic Acid 0.5
Ultranox 626 0.8 Protox 169 ZnO
3.5 Sunpar 150 Oil
21.5
Protox 169 ZnO 0.8 SP 1056 Resin
3.0 Irganox 3114 0.5
SP 1056 Resin 4.0 Ultranox 626 0.8
Protox 169 ZnO
2.2
SP 1056 Resin 3.5
__________________________________________________________________________
TABLE III
__________________________________________________________________________
Effect of Elastomer Blend Ratio: Bromobutyl/EPDM
CONTROL
INVENTION
12 13 14 15
__________________________________________________________________________
Vistalon 3777 (EPDM: Oil 57:43)
50 25 15 10
Bromobutyl 2244 -- 21 29.4 33.6
Maglite D Magnesium Oxide
-- 0.3 0.4 0.4
PP 5052 Polypropylene
16.7 17.35
17.61
17.74
Nucap 190 Clay 8.2 5.8 4.96 4.44
Titanox 2071 1.0 2.0 2.4 2.6
Sunolite 127 Wax 1.5 0.75 0.45 0.3
Stearic Acid 0.5 0.45 0.45 0.5
Sunpar 150 Oil 16.0 22.0 24.4 25.6
Vanox MTI -- 0.3 0.3 0.4
Irganox 3114 0.5 0.25 0.15 0.1
Ultranox 626 0.8 0.4 0.24 0.16
Protox 169 Zinc Oxide
0.8 1.9 2.34 2.56
SP 1056 Resin 4.0 2.0 1.2 0.8
HVA-2 -- 0.5 0.7 0.8
PROPORTIONS
% of pre-formed dynamically
-- 50% 30% 20%
vulcanized EPDM compound (12) used
as a masterbatch in the final compound
Ratio of Bromobutyl to EPDM
0:100 59.5:40.5
77.4:22.6
85.5:14.5
FLOW PROPERTIES 21 23 23 23
Spiral Flow, cm
PHYSICAL PROPERTIES
Injection Molded,
Die Cut Dumbbells:
Hardness, Shore A, Inst./10 sec.
70/67 70/67
70/67
69/66
100% Modulus, psi 460 460 460 460
Tensile Strength, psi
1020 1090 1040 1040
Elongation, % 460 350 320 320
Tear Strength, Die B, pli
170 140 120 130
THERMAL STABILITY
Compression Set B, %
63 44 41 38
22 Hr. @ 100.degree. C.
High Temperature Aging:
Air Oven Aging, 2 Wks. @ 150.degree. C.
Hardness Change, Points
+8 +3 +1 +2
% Tensile Retained 55 102 96 97
% Elongation Retained
9 91 90 97
Air Oven Aging, 4 Wks. @ 150.degree. C.
Hardness Change, Points
+24 +5 +3 +3
% Tensile Retained 49 92 90 95
% Elongation Retained
0.2 75 74 86
Air Oven Aging, 45 Days @ 150.degree. C.
Hardness Change, Points
+5 +8 +4 +1
% Tensile Retained 51 66 84 81
% Elongation Retained
0 47 80 80
Air Oven Aging, 60 days @ 150.degree. C.
Hardness Change, Points
+5 +8 +4 +4
% Tensile Retained 27 47 77 74
% Elongation Retained
0 22 61 67
ASTM #3 Oil, 70 Hr. @ 100.degree. C.
Volume Swell, % 123 97 87 88
% Tensile Retained 45 55 62 49
% Elongation Retained
36 44 53 37
__________________________________________________________________________
TABLE IV
__________________________________________________________________________
Effect of Elastomer Blend Ratio, Bromobutyl:EPDM
CONTROL
INVENTION
16 17 18 19
__________________________________________________________________________
Vistalon 3777 (EPDM: Oil 57:43)
50 25 15 10
Bromobutyl 2244 -- 21 29.4 33.6
Maglite D Magnesium Oxide
-- 0.3 0.4 0.4
PP 5052 Polypropylene
16.7 17.35
17.61
17.74
Nucap 190 Clay 8.8 6.1 5.14 4.56
Titanox 2071 1.0 2.0 2.4 2.6
Sunolite 127 Wax 1.5 0.75 0.45 0.3
Stearic Acid 0.5 0.45 0.45 0.5
Sunpar 150 Oil 16.0 22.0 24.4 25.6
Vanox MTI -- 0.3 0.3 0.4
Irganox 3114 0.5 0.25 0.15 0.1
Ultranox 626 0.8 0.4 0.24 0.16
Protox 169 Zinc Oxide
3.0 3.0 3.0 3.0
Sulfur 0.2 0.1 0.06 0.04
DPTTS 0.4 0.2 0.12 0.08
MBT 0.6 0.3 0.18 0.12
HVA-2 -- 0.5 0.7 0.8
PROPORTIONS
% of pre-formed dynamically
-- 50% 30% 20%
vulcanized EPDM compound (16) used
as a masterbatch in the final compound
Ratio of Bromobutyl to EPDM
0:100 59.5:40.5
77.4:22.6
85.5:14.5
FLOW PROPERTIES 19 26 24 24
Spiral Flow, cm
PHYSICAL PROPERTIES
Injection Molded,
Die Cut Dumbbells:
Hardness, Shore A, Inst./10 sec.
70/67 70/66
69/65
64/64
100% Modulus, psi
Tensile Strength, psi
810 980 900 1030
Elongation, % 350 330 280 290
Tear Strength, Die B, pli
170 120 120 120
THERMAL STABILITY
Compression Set B, %
43 33 35 33
22 Hr. @ 100.degree. C.
High Temperature Aging:
Air Oven Aging, 2 Wks. @ 150.degree. C.
Hardness Change, Points
+3 +2 +5 +5
% Tensile Retained 123 100 110 85
% Elongation Retained
91 84 96 82
Air Oven Aging, 4 Wks. @ 150.degree. C.
Hardness Change, Points
+6 +2 +3 +5
% Tensile Retained 102 104 104 94
% Elongation Retained
40 80 84 83
Air Oven Aging, 6 Wks. @ 150.degree. C.
Hardness Change, Points
+18 +9 +9 +11
% Tensile Retained 36 76 70 96
% Elongation Retained
0.6 49 93 95
ASTM #3 Oil, 70 Hr. @ 100.degree. C.
Volume Swell, % 94 82 79 79
% Tensile Retained 65 58 72 61
% Elongation Retained
46 42 56 50
__________________________________________________________________________
TABLE V
__________________________________________________________________________
DVAs With a Minor Amount of Pre-formed Dynamically Vulcanized EPDM
Contrasted with DVAs Containing Bromobutyl Only or Bromobutyl Plus
Uncured EPDM
INVENTION: DVA with Bromobutyl
CONTROL with
CONTROL plus a pre-formed dynamically
Bromobutyl and a pre-
only Bromobutyl
vulcanized EPDM composition
formed uncured EPDM
20 21 22 23
__________________________________________________________________________
Bromobutyl 2244 42 33.6 33.6 33.6
Dynamically vulcanized EPDM composition
-- 20 -- --
Santoprene 201-73 -- -- 20 --
EPDM composition -- -- -- 20
Maglite D Magnesium Oxide
0.5 0.4 0.4 0.4
PP 5052 Polypropylene 18 14.4 14.4 14.4
Nucap 190 Clay 3.5 2.8 2.8 2.8
Titanox 2071 3.0 2.4 2.4 2.4
Sunolite 127 Wax -- -- -- --
Stearic Acid 0.5 0.4 0.4 0.4
Sunpar 150 Oil 28 22.4 22.4 22.4
Vanox MTI 0.5 0.4 0.4 0.4
Irganox 3114 -- -- -- --
Ultranox 626 -- -- -- --
Protox 169 Zinc Oxide 3.0 2.4 2.4 2.4
HVA-2 1.0 0.8 0.8 0.8
PROPORTIONS
% of pre-formed dynamically
-- 20% 20% None (20% of
vulcanized EPDM composition used non-vulcanized EPDM
as a masterbatch in the final compound composition added)
Ratio of Bromobutyl to EPDM
100:0 85.5:14.5 unknown 85.5:14.5
FLOW PROPERTIES 26 24.5 26 30
Spiral Flow, cm
PHYSICAL PROPERTIES
Injection Molded,
Die Cut Dumbbells:
Hardness, Shore A, Inst./10 sec.
70/65 70/64 71/65 72/67
100% Modulus, psi 580 620 580 580
Tensile Strength, psi 860 1130 1050 960
Elongation, % 230 290 280 250
Tear Strength, pli 120 140 140 130
THERMAL STABILITY
Compression Set B, % 42 41 42 44
22 Hr. @ 100.degree. C.
High Temperature Aging:
Air Oven Aging, 2 Wks. @ 150.degree. C.
Hardness Change, Points
+1 -3 +2 0
% Tensile Retained 81 88 85 98
% Elongation Retained 71 87 81 99
Air Oven Aging, 4 Wks. @ 150.degree. C.
Hardness Change, Points
+6 + 7 +9 +5
% Tensile Retained 74 81 83 96
% Elongation Retained 65 79 78 102
Air Oven Aging, 8 Wks. @ 150.degree. C.
Hardness Change, Points
+8 +8 +11 +7
% Tensile Retained 42 57 75 77
% Elongation Retained 27 48 79 91
ENVIRONMENTAL RESISTANCE
ASTM #3 Oil, 70 Hr. @ 100.degree. C.
Volume Swell, % 68 82 69 82
% Tensile Retained 56 61 60 60
% Elongation Retained 68 53 52 55
__________________________________________________________________________
TABLE VI
__________________________________________________________________________
DVA BLENDS HAVING EPDM:BROMOBUTYL 50:50
DVA Based
DVA Based
DVA Based
on EPDM
on EPDM
on EPDM
24 25 26 27 28 29 30
__________________________________________________________________________
Vistalon 3666 (EPDM:oil 57:43)
26.25
26.25
-- 26.25
Vistalon 6630 (EPDM:oil 77:23)
-- -- 19.50
--
Bromobutyl 2244 15.00
15.00
15.00
15.00
Black Carbon SRF 762
10.43
10.43
9.90
10.03
PP Copolymer 7824
15.40
15.40
15.40
15.40
Neutral 600 Oil -- 23.57
-- --
Sunpar 2280 Oil 23.57
-- 30.45
23.57
Ultranox 626 0.05
0.05
0.05
0.05
Irganox 1010 0.20
0.20
0.20
0.20
Wax Antilux 1.60
1.60
1.00
1.00
Maglite D 0.20
0.20
0.20
0.20
Stearic Acid 0.40
0.40
0.40
0.40
Zinc Oxide 3.00
3.00
3.00
3.00
HVA 2 -- -- 1.00
1.00
SP 1056 3.30
3.30
3.30
3.30
SnCl.sub.2.H.sub.2 O
0.60
0.60
0.60
0.60
Physical Properties On
Die Cut Samples
Hardness, Shore A - Instant.
76 71 73 73 61 70 78
5" 67 68 70 70 57 67 76
30" 65 66 67 68 55 65 74
100% Modulus, psi
406 414 420 414 239 392 479
Tensile Strength, psi
980 950 936 1016 464 697 805
Elongation, % 330 307 306 324 270 284 323
Tear Strength, Die C, pli
160 147 140 141 114 138 165
Compression Set B, % at 100.degree. C.
39 38 42 39 30 34 40
Injection-Moulded
good
good
good
good trace good good
Plates Surface Quality imperfections
Ratio of Bromobutyl Rubber
50:50
50:50
50:50
50:50
to EPDM
__________________________________________________________________________
TABLE VII
__________________________________________________________________________
31 32 33 34 35 36 37 38
__________________________________________________________________________
Vistalon 3666 (EPDM:oil 57:43)
26.80
26.80
26.80
52.35
-- 50/50
-- 50/50
Bromobutyl 2244 15.30
15.30
15.30
-- 31.00
blend of
31.00
blend of
Vistalon 808 -- -- -- -- -- 34 and 35
5.00
34 and 37
PP PPH 1050 15.72
15.80
15.80
15.40
16.90 16.90
SRF 762 10.30
10.90
10.90
10.30
12.55 7.55
Sunpar 2280 Oil 23.00
23.00
23.00
12.00
35.20 35.20
Ultranox 626 0.05
0.10
0.10
0.05
0.05 0.05
Irganox 1010 0.20
0.20
0.20
0.20
0.20 0.20
Wax Antilux 1.60
1.60
1.60
1.60
1.60 1.60
Maglite D 0.20
0.20
0.20
0.20
0.20 0.70
Stearic Acid 0.40
0.40
0.40
0.40
0.40 0.40
Zinc Oxide 3.00
3.00
3.00
2.65
1.50 1.50
HVA-2 2.40
2.40
1.50
2.57
0.30 0.30
Perkadox 14/40 Peroxide
1.00
0.40
0.20
1.80
-- --
Physical Properties On
Die Cut Samples
Hardness, Shore A - Instant.
76 76 76 70 72 71 72 70
5" 73 73 73 67 67 66 67 64
30" 71 71 71 65 64 64 64 62
100% Modulus, psi
460 508 450 392 385 392 385 348
Tensile Strength, psi
710 827 926 740 675 856 675 791
Elongation, % 207 224 333 235 217 280 271 330
Tear Strength, Die C, pli
155 166 160 143 109 132 160 155
Compression Set B, % at 23.degree. C.
22 23 27 20 23 20 26 22
100.degree. C.
38 41 44 37 41 40 40 40
Ratio of Bromobutyl Rubber to
50:50
50:50
50:50
0:100
100:0
40.8:49.2
100:0
50.8:49.2
Crosslinked EPDM
__________________________________________________________________________
TABLE VIII
______________________________________
Test Test Method
______________________________________
Shore A Hardness, instantaneous
ASTM D2240
5 sec.
30 sec.
100% Modulus, psi ASTM D412
300% Modulus, psi ASTM D412
Tensile Strength, psi
ASTM D412
Elongation, % ASTM D412
Tear Strength, pli
Compression Set B, %
ASTM D395
22 Hr. @ 100.degree. C.
22 Hr. @ 150.degree. C.
Volume Swell, % ASTM D-471
Hardness Change, points
ASTM D2240
Spiral flow, cm @ 800 psi
Length of filled portion of a
spiral-shaped mold having
mold pathway of 0.3 cm
diameter at 260.degree. C.
MFR @ 230.degree. C., 10K g
ASTM D1238
______________________________________
TABLE IX
______________________________________
Blend Components
Component
______________________________________
Bromobutyl 2244
Brominated isoprene-isobutylene
copolymer, 41-51 Mooney viscosity
(1 + 8) 125.degree. C.
[Exxon Chemical]
FLEXON 845 Paraffinic oil ASTM D2226 type
104B
[Exxon Company, USA]
HVA-2 N,N-m-phenylenedimaleimide - [E. I. DuPont]
IRGANOX 1010 Hindered phenolic antioxidant,
thermal stabilizer [CIBA-GEIGY]
MAGLITE D Magnesium Oxide [C. P. Hall Co.]
NEUTRAL 600 Extracted paraffinic oil
[Exxon Company, USA]
NUCAP 190 CLAY
Mercapto silane functional hydrated
aluminum silicate
[J. M. Huber Corp.]
PERKADOX 14/40
40% a,a'bis(t-butylperoxy) diisopropyl
benzene on clay filler
[Akzo Chemie]
PP COPOLYMER Polypropylene copolymer, 0.5 MFR
PPH 1022 [Hoechst]
PP COPOLYMER Random reactor copolymer of
7824 propylene with minor amount
ethylene, MFR of 0.4
[Neste Polypropylen N.V.,
Beringen, Belgium]
PP HOMOPOLYMER
Polypropylene homopolymer 0.3 MFR
PPH 1050 [Hoechst]
PP 5052 Polypropylene homo-polymer,
density 0.90 g/cm.sup.3, MFR 1.2
[Exxon Chemical]
PROTOX 169 French process zinc oxide
[New Jersey Zinc]
SANTOPRENE Thermoplastic elastomer based
on EPDM in polypropylene
[Monsanto]
SnCl.sub.2.H.sub.2 O
Tin chloride monohydrate [Any]
SP 1056 Brominated alkyl phenol resin
[Schenactady Chemical]
SRF 762 Carbon black [Cabot]
Stearic Acid Long chain fatty acid
SUNPAR 150 Paraffinic oil
[Sun Oil Company]
SUNPAR 2280 Paraffinic Oil
[Sun Oil Co.]
TITANOX 2071 Titanium dioxide
[NL Industries, Inc.]
TRANSLINK 37 Calcined and surface modified kaolin
[KMG Minerals, Inc.]
ULTRANOX 626 Bis (2,4-di-tert-butylphenyl)
pentaerythritol diphosphite
[Borg-Warner Chemicals, Inc.]
VANOX MTI 2-mercaptotoluimidizaole
[R. T. Vanderbilt Co., Inc.]
VANOX PML Di-ortho guanidine salt of
dicathechol borate
[R. T. Vanderbilt Co., Inc.]
VISTALON 3666 Ethylene-propylene-ethylidene
norbornene product, 49 Mooney
viscosity (1 + 8) 127.degree. C.
[Exxon Chemical]
VISTALON 6630 Ethylene-propylene-ethylidene
norbornene product, 31 Mooney
viscosity (1 + 8) 127.degree. C.
[Exxon Chemical]
VISTALON 808 Ethylene-propylene copolymer,
40 Mooney viscosity (1 + 8)
127.degree. C. [Exxon Cbemical]
WAX ANTILUX Blend of selected paraffins and
microwaxes [Rhein Chemie]
ZnO Zinc oxide [Any source, e.g.
New Jersey Zinc]
______________________________________
Although the invention has been described with reference to its preferred
embodiments, those of ordinary skill in the art may, upon reading this
disclosure, appreciate changes and modifications which may be made which
do not depart from the scope and spirit of the invention as described
above or claimed hereafter.
Top